Feb., 1941
HYDROGENATION OF LIGNIN
same conditions p-iodophenyl phenyl ether is metalated in reactions with n-butyllithium and phenyllithium. p-Fluoro-, D-chloro- and fi-bromoanisoles are metalated by- methyllithium. Under the same conditions o- and m-bromo- and o- and p-iodo-
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anisoles undergo some halogen-metal interconversion followed by coupling, which results in appreciable yields of methyl tolyl ethers.
~~~~~~~: AMES,IOWA
RECEIVED OCTOBER21, 1940
[A COM~~~NICATION FROM THE LABORATORY OF ORGANIC CHEMISTRY OF THE UNIVERSITY OF WISCONSIN ]
The Products of the Hydrogenation of Lignin' BY HOMERADKINS.ROBERT L .FRANKAND EDWARD S. BLOOM 8.
The first paper of this series described experimental work in which lignin, extracted from freshly cut aspen, was converted by hydrogenation over copper chromite to a mixture of saturated, colorless compounds.2.a At least 75% of the lignin was converted to water, methanol and derivatives of propylcyclohexane. The predominance of hydroxy derivatives of propylcyclohexane among the products of the hydrogenation supported the hypothesis that lignin is a polymer in which the primary unit contains nine carbon atoms. However, the isolation of compounds of such low molecular weight does not show how they were joined together in the lignin molecule. It therefore seemed of importance to study the products of the hydrogenation of types of lignin which gave larger proportions of compounds containing more than nine carbon atoms to the molecule. A survey in this Laboratory of the behavior of different types of lignin has shown that lignins obtained from either hard or soft woods, by either the soda or sulfite process, give a much lower yield of nine carbon atom compounds than did the lignin extracted with methanol from freshly cut aspen. Attention has therefore been concentrated upon a sample of lignin produced by the Meade Company of Chillicothe, Ohio, from a mixture of hard woods, using the soda process.* (1) This investigation was supported in part by funds given by the Wisconsin Alumni Research Foundation. (2) Harris, D'Iann' and Adkins, THISJOURNAL, 60, 1467 (1938). (3) Credit should have been given in the first paper to Dr. Harold Hibbert of McGill University, who supplied the sample of lignin on which the first successful hydrogenation of lignin over copper chromite was accomplished. The mixture of products resulting from the hydrogenation was returned to him. The method and process used by me on the sample of lignin submitted by Dr. Hibbert was the same as that used almost a year later on a sample prepared by Dr. Harris. A patent has been obtained by Messrs. Earl C. Sherrard and Elwin E . Harris (application May 10, 1938, issued February 7, 1939, number 2,146,655) which attempts to cover the process of hydrogenating lignin over copper chromite.-H. A. (4) We arc indebted to Mr. Gaston DuBois of the Mensanto Chemical Company for our supply of Meade Lignin.
The Meade lignin is a cocoa-like reddish-brown powder which according to an analysis by Dr. Carl Tiedcke of New York City contains 23.3% methoxyl, 6
